1. Field of the Invention
The present invention relates to a wrench having a pawl that is supported at two rigid areas.
2. Description of the Related Art
Ring spanners can be used in a limited space, e.g., an engine room of a vehicle, as they have been developed to overcome the problem of insufficient torque-bearing capacity. FIG. 12 of the drawings illustrates conventional ratchet type ring spanner comprising a handle 1, a gear wheel 4 rotatably mounted in a space of a head extended from an end of the handle 1, and a pawl 3 mounted in a cavity 2 of the handler 1. When the handle 1 is turned along a direction indicated by the arrow, an end of the pawl 3 bears against a side wall defining a portion of the cavity 2 and thus runs the gear wheel 4 for tightening/loosening a fastener. Namely, the pawl 3 is supported at a single supporting area. However, the inner lateral side of the pawl 3 facing away from the gear wheel 4 is not supported at all. Thus, the other lateral side 3a of the pawl 3 facing the gear wheel 4 pivots about a supporting point in the supporting area and slightly disengages from the teeth of the gear wheel 4 when a force exerting on the pawl 3 exceeds a predetermined value. As a result, a seesaw effect is incurred on the pawl 3 which leads to a poor engagement between the pawl 3 and the gear wheel 4; namely, the pawl 3 merely engages with the gear wheel 4 by the first three teeth, which tends to cause damage to these three teeth. Such a conventional ratchet type ring spanner of 17 mm size can bear a torque of about 28 kg-m. A solution to increase the torque-bearing capacity is to increase the size of the pawl, yet this contradicts the advantage of spanners for use in limited spaces, as the size of the head is also increased. FIG. 13 of the drawings illustrates another conventional wrench including a pawl 6 mounted in a cavity 8 of a handle (not labeled) for engaging with a gear wheel 7 in a head 5 extended from the handle. The pawl 6 includes a toothed side having two toothed portions 6a and 6b that have different centers of curvatures for meshing with the teeth of the gear wheel 7 by more teeth. The torque-bearing capacity of the pawl 6 is increased by about 30% when compared with the pawl of the wrench in FIG. 12 having the same size. However, the torque-bearing capacity of the pawl is still improvable without increasing the size of the pawl and the size of the head.
An object of the present invention is to provide a wrench having a pawl that is supported at two rigid areas, thereby providing a higher torque-bearing capacity without increasing the size of the pawl and the size of the head of the wrench.
Another object of the present invention is to provide a wrench including a pawl having a toothed side, wherein all of the teeth of the toothed side reliably mesh with the teeth of a drive member of the wrench, thereby providing a higher torque-bearing capacity.
A wrench in accordance with the present invention comprises a handle having a cavity defined by a wall. A head extends from the handle and comprises a compartment that is communicated with the cavity. A drive member is rotatably received in the compartment of the head and comprises a plurality of teeth on an outer periphery thereof. A pawl is received in the cavity of the handle and engaged with the teeth of the drive member. The pawl is supported by two fixed rigid supporting areas when in an operative position for ratcheting operation.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.